This invention relates to one key chording systems for electronic keyboard instruments in which actuation of a single key on a standard keyboard causes the sounding of a complete musical chord rather than a single note at a single pitch or multiple pitches.
Prior art systems for accomplishing one key chording on a standard keyboard have typically involved either A.C. keying of chord tone signals using multiple contacts associated with each key of the keyboard, or D.C. keying of chord tone signals. Early examples of one key chording systems employing D.C. keying are Bohm U.S. Pat. No. 3,681,508 and Southard U.S. Pat. No. 3,740,449, and more recent examples are illustrated in Robinson et al U.S. Pat. No. 3,725,560 and Schreier U.S. Pat. No. 4,000,674.
In the system disclosed by Robinson et al, the signals from the keyswitches operated by the playing keys are routed to gates and the signals from the gates are then routed through inverters to the control terminals of the keyers. In the conventional playing mode, the signal from each actuated keyswitch is routed through a gate to a single inverter and, when the organ is adjusted to play chords, the signal from each of the chord playing keys of the lower manual is routed to a group of gates with the signals from the group of gates being connected to a group of the aforementioned inverters to supply actuating signals to a plurality of the keyers, thereby making up a musical chord. The switching employed for selecting between the chord playing mode and the conventional mode is accomplished by D.C. logic and control of the keyers is also achieved by D.C. logic.
The one key chording system disclosed in U.S. Pat. No. 4,000,674 is designed for use in an electronic keyboard instrument employing single contact keyswitches for D.C. keying of tone signals. A primary keying signal from an actuated keyswitch operates one of a plurality of chord gates to produce a chord keying signal which is translated by one of a set of chord logic units into secondary keying signals. The primary and secondary keying signals operate keyers for tone signals corresponding to a musical chord. The chord gates are activated at all times and an inhibit circuit under control of a mode control circuit prevents the chord gates from responding to secondary keying signals thereby to switch the single key chording system off to return the instrument to normal operation.
Another known one key chording system is the "Magic Genie Chords" system used in the Lowrey organ and described in the Service Manual for Lowrey's Model TG-1. This system has the capability of playing forty-eight chords semi-automatically utilizing thirteen keys of the lower manual plus a foot switch on one side of the expression pedal of the organ. The twelve major chords of the musical scale can be produced by playing only one key at a time, with the name of the key depressed always corresponding to the name of the chord produced. The second lowest A key (A2) is reserved for changing any one-finger chord from a major chord to a dominant seventh chord; that is, simultaneous actuation of the C and A2 keys will produce a C dominant seventh chord, or depressing a D key and a A2 key simultaneously will produce a D dominant seventh chord, etc. Either major or dominant seventh chords may be changed to minor chords by simultaneously depressing the aforementioned foot switch on the expression pedal.
It is the primary object of the present invention to provide a one key chording system for a D.C. keyed electronic keyboard instrument which utilizes the same keyboard contacts and D.C. keyers that are employed in the normal multiple key chording operation of the instrument, which has the same chord-playing capability as the Lowrey system but whose implementation is simpler than any of the referenced prior art systems, thereby enabling provision of this feature on an electronic keyboard instrument at minimum cost.